M14/0311 said:
I have a '95 XJ 4.0 and this thing eats coils. Have owned it for 14 months and have gone through 5 coils. Put a new one on and it last anywhere from 2-3 hours. HELP ! Where do I start looking/checking ???
Have you changed the rotor, cap and plug wires yet? If one or more of them has too high a resistance it could be causing the coil to load up (overload) and look for an alternate path to ground until it finds or makes one, thus burning (shorting) it out. Could also be the ICM (Igniton Coil Modile, electronic) directly under the HV coil) is bad and hiting the coil with too much voltage, thus overloading the coil to burn out. I think the ICM voltage output and input from the CPM(ECU) (with the HV coil removed) can be tested with DMM to see if this is case, while in the run (but do not start mode). As I recall the HV coil has power to the input side and the spark is initiated by ground that low voltage on the coil, which causes a field colapse on the secondary HV side, thus causing the spark.
I would quess that there is bad common supplier of HV coils causing the problem, but I would check and replace (if you have not done so already) the rotor, cap, and HV coils.
I would also find a good, old HV coil, and try it, if it burns up quickly then I would suspect the ICM and or PCM (ECU), (or maybe a shorted wiring harness sending the wrong voltage to coil, like 14 volts instead of 5 volts). I don't recall the coil input volatge, but I am thinking 5 volts for some reason is or was common, so if this is the case a 14 volt signal would cause too high a coil voltage and burn it out.